1. Field of the Invention
The present invention relates to a light source unit and a projector.
2. Description of the Related Art
In these days, data projectors are used on many occasions as image projection apparatuses which project images including images of screens of personal computers and video images, as well as images based on image data which is stored in memory cards on to a screen.
Conventionally, the mainstream of these projectors has been those which use a high-intensity discharge lamp as a light source. However, in recent years, there have been made many developments and proposals on projectors which use, as a light source, a light emitting diode (LED), a laser beam emitting device, a device utilizing organic EL technology and a luminescent material.
For example, Japanese Unexamined Patent Publication No. 2004-341105 (JP-A-2004-341105) proposes a light source unit which produces light source light of red, green and blue wavelength bands. In this light source unit, red, green and blue luminescent material layers are provided in an end-to-end fashion on a surface of a luminescent plate made up of a disc having transmissivity, and a dichroic filter which transmits ultraviolet radiation and reflects visible light is disposed on aback side of the luminescent plate. In this construction, by shining ultraviolet light on to the luminescent material layers from the back side of the luminescent plate, light source light of red, green and blue wavelength bands is produced from the light source unit.
In addition, in the previous patent application (Japanese Patent Application No. 2009-155458: not prior art) the applicant of this patent application proposed the light source unit which includes the blue laser emitting element, the red light emitting diode and the luminescent wheel which has the green luminescent material layer emitting light of green wavelength band when receiving light emitted from the blue laser emitting element as excitation light and on which the diffuse transmission plate which diffusely transmits light emitted from the blue laser emitting element is provided in the circumferential direction.
In this light source unit, light source light of red wavelength band is produced by the red light emitting diode, and light source light of green wavelength band is produced by shining light emitted from the blue laser emitting element on to the green luminescent material layer on the luminescent wheel as excitation light. In addition, by causing light emitted from the blue laser emitting element to be diffuse transmitted through the diffuse transmission plate, light source light of blue wavelength band is produced.
In the light source unit according to the patent application filed by the applicant of this patent application, the optical paths of light of red wavelength band, light of green wavelength band and light of blue wavelength band are different from one another. Therefore, the optical layout becomes complex when attempting to cause the directions of optical axes of light of red wavelength band, light of green wavelength band and light of blue wavelength band to coincide with each other so as to be shone on to the display device.
In addition, the optical layout becomes complex, and therefore, the numbers of lenses and mirrors are increased, which disturbs the attempt to reduce the production costs, as well as to make the projector small in size.
Additionally, light of red wavelength band is produced by the red light emitting diode, and therefore, in order to increase the quantity of light of red wavelength band, a red light emitting diode which is large in size needs to be used or the number of red light emitting diodes needs to be increased.
Consequently, the solutions to the complex layout and the attempt to increase the quantity of light of red wavelength band cause disturbance to ensuring the degree of freedom in designing projectors which are small in size and which consume less electric power.